LUCINA 



to a remarkable incrassation of the shell within the mus- 

 cular impression of the mantle^ probably caused by age, 

 and the surface of this incrassated substance is often 

 covered by deeply impressed dots : and in some fossil 

 species, when broken, it is found to consist of close set, 

 laterally aggregated, short, perpendicular fibres. 



The species of this Genus are not very numerous; 

 the most beautiful are unquestionably the L, Tigerina and 

 L, 'punctata; the L, Jamaicensis and h, Radula have each 

 a very elongated anterior muscular impression, and the 

 L. Pennsylvanica has a most beautiful crisped epidermis. 

 Of the British species the principal is the L. Radula, and 

 there are several smaller sorts common to our shores.* 

 There are many fossil species that occur commonly in 

 the tertiary beds, of which they appear to be charac- 

 teristic. One of these, the L, mutabilis, Lam. is remark- 

 ably flat and irregularly expanded; and another that 

 is common at Bordeaux is as singularly globular in its 

 form. 



Fig. 1 . Lncina punctatat inside. 



2. Jamaicensis, inside. 



3. Childreniy inside. 



4. Pennsylvanica, to show its epidermis. 



5. mutahilis, inside. 



6. Columhella, to show the globular form and the teeth. 



♦ Of these the L.lactea^ Lam. is one; if we may judge from the repetition 

 of the Synonyms, this shell which is a true Lucina, is twice repeated by La- 

 marck among his Amphidesmata under the names of A. iactea and A. Lncinalis. 



